1. Field of the Invention
The present invention relates to a Radio Frequency Identification, (hereinafter RFID) tag and more particularly, to an RFID tag having an internal antenna.
2. Description of the Related Art
An RFID system generally includes an RFID tag attached on an object, which transmits a wireless signal having intrinsic identification information of itself, and an RFID reader receiving the transmitted wireless signal from the RFID tag and analyzing the signal.
The RFID tag includes a passive RFID tag and an active RFID tag. One of the active RFID tags uses a frequency of 433 MHz. The active RFID tag is used in diversity areas including logistics in harbors, aviation, military, and Ubiquitous Sensor Network. The active RFID tag typically has a helical antenna wound a conducting wire wound in a helical shape.
In a case that an active RFID tag is attached on a front surface or a lateral surface of a large object, e.g., a container, an RFID reader of the conventional RFID system may recognize the active RFID tag. However, in a case that the active RFID is attached on a back side of the large object, the RFID reader of the RFID system may not recognize the RFID tag. Because an electric field generated by the helical antenna in the active RFID tag is hidden by the large object, the RFID reader of the RFID system may not recognize the active RFID tag. That is, the electric field by the helical antenna is hidden by the large object since the helical antenna is a vertically polarized antenna, such that the communication between the RFID reader and RFID tag may not be implemented. Further, in a case that the active RFID tag is attached on the large object, a radiation pattern of the electric field caused by the helical antenna may be distorted. That distortion may decrease efficiency of the RFID system.